This application discloses subject matter related to subject matter disclosed in co-pending U.S. patent applications: Ser. No. 09/496,341, filed on Feb. 2, 2000; Ser. No. 09/634,253, filed Aug. 7, 2000; Ser. No. 09/612,319, filed on Jul. 7, 2000; Ser. No. 09/433,377, filed on Nov. 3, 1999; Ser. No. 09/433,375, filed on Nov. 3, 1999; Ser. No. 60/109,230, filed on Nov. 18, 1998; Ser. No. 09/433,378, filed on Nov. 3, 1999; and Ser. No. 09/421,393, filed on Oct. 20, 1999, incorporated herein by reference.
The present invention relates to the recording, storage and reading of magnetic data, particularly rotatable recording media, such as thin film magnetic disks having smooth surfaces for data zone. The invention has particular applicability to high density recording media exhibiting low noise and having improved flying stability, glide performance and head-media interface reliability for providing zero glide hits.
Magnetic disks and disk drives are conventionally employed for storing data in magnetizable form. Typically, one or more disks are rotated on a central axis in combination with data transducing heads positioned in close proximity to the recording surfaces of the disks and moved generally radially with respect thereto. Magnetic disks are usually housed in a magnetic disk unit in a stationary state with a magnetic head having a specific load elastically in contact with and pressed against the surface of the disk.
Data are written onto and read from a rapidly rotating recording disk by means of a magnetic head transducer assembly that flies closely over the surface of the disk. It is considered desirable during reading and recording operations to maintain each transducer head as close to its associated recording surface as possible, i.e., to minimize the flying height of the head. This objective becomes particularly significant as the areal recording density increases. The areal density (Mbits/in2) is the recording density per unit area and is equal to the track density (TPI) in terms of tracks per inch times the linear density (BPI) in terms of bits per inch.
The increasing demands for higher areal recording density impose increasingly greater demands on flying the head lower because the output voltage of a disk drive (or the readback signal of a reader head in disk drive) is proportional to 1/exp(HMS), where HMS is the space between the head and the media. Therefore, a smooth recording surface is preferred, as well as a smooth opposing surface of the associated transducer head, thereby permitting the head and the disk to be positioned in closer proximity with an attendant increase in predictability and consistent behavior of the air bearing supporting the head.
In recent years, considerable effort has been expended to achieve high areal recording density. Among the recognized significant factors affecting recording density are magnetic remanance (Mr), coercivity, coercivity squareness (S*), signal/noise ratio, and flying height, which is the distance at which a read/write head floats above the spinning disk. Prior approaches to achieve increased areal recording density for longitudinal recording involve the use of dual magnetic layers separated by a non-magnetic layer as in Teng et al., U.S. Pat. No. 5,462,796, and the use of a gradient magnetic layer interposed between two magnetic layers as in Lal et al., U.S. Pat. No. 5,432,012.
However, the goal of achieving a rigid disk recording medium having an areal recording density of about 100 Gb/in2 has remained elusive. In particular, the requirement to further reduce the flying height of the head imposed by increasingly higher recording density and capacity renders the disk drive particularly vulnerable to head crash due to accidental glide hits of the head and media. To avoid glide hits, an accurately controlled movement of the head and a smooth surface of data zone are desired.
Conventional methods for accurately controlling the movement of the head use servo writers. Servo writer is a device which write xe2x80x9cservo patternxe2x80x9d on the disk surface.
Conventional techniques for producing a smooth surface on the disk include polishing and tape burnishing (buffing). See, for example, Nakamura et al., U.S. Pat. No. 5,202,810 and Bornhorst et al., U.S. Pat. No. 4,430,782. Typically, the polishing is done using a slurry and buffing is done after sputtering. However, these conventional techniques are attendant with numerous disadvantages. For example, it is extremely difficult to provide a clean and smooth surface due to debris formed by mechanical abrasions.
There exists a need for a recording medium having an areal recording density in excess of 10 Gb/in2, such as in the 20 Gb/in2 range, preferably up to 400 Gb/in2, exhibiting high coercivity and coercivity squareness and a relatively low Mrt (magnetic remanance x thickness), which could be employed for hard disk drives using GMR (giant magnetoresistance) heads. For a GMR media, there exists a need to reduce the fly height to below 1 microinch (25 nm) with zero glide hits.
Disk glide height test (glide hits, glide avalanche), head fly height, and recording performance (output voltage, half peak height PW50, signal-to-noise ratio SNR) are sensitive to the spacing between the head and media. Also, the conventional servo writers have a TPI (tracks per inch) limit. The limit of TPI of conventional servo writers is about 50 KTPI. Exceeding this limit causes inaccurate position of head, i.e. head cannot fly accurately on the desired track.
Accordingly, there exists a need for a system capable of providing a controlled movement of the head on the substrate of a magnetic disk, thereby providing zero glide hits to enhance the reliability, tribology and long term durability of the data storage device.
An object of the present invention is a recording medium comprising a substrate having a surface of data zone with an embossed pattern on a solgel layer on the substrate to provide Pattern Assisted Magneto-Recording (PAMR) media. The PAMR media is capable of providing zero glide hits, enhanced head-media interface reliability, tribology and glide performance of the head. Solgel is a SiO2-containing material capable of forming a thin film on a substrate. The thickness of the thin film that forms a sol gel layer could be in the range of a few angstroms to a few millimeters. A xe2x80x9cservo patternxe2x80x9d could be formed on a solgel surface. A stamper could be used to emboss the patterns on the solgel layer. The pattern could be a combination of dots, lines, and grooves in either radial direction, or circumferential direction, or spiral direction. The pattern could help the recording head and actuator to search for the position of sectors and tracks.
Another object of the invention is a method of preparing the PAMR media.
Additional advantages and features of this invention will be set forth in part in the description that follows and in part will become apparent to those having ordinary skill in the art upon examination of the following description and from the knowledge gained by practicing the invention. The advantages of this invention may be realized and obtained and are particularly pointed out in the claims.
According to the present invention, the foregoing and other objects are achieved in part by a recording medium comprising a substrate and a solgel layer on the substrate, wherein the solgel layer comprises a pattern.
Another embodiment is a recording medium comprising a substrate and a pattern-assisted means for controlled movement of a head of the recording medium on the substrate. The pattern-assisted means for controlled movement of the head could be a pattern on the surface of the substrate. The pattern is not limited to any particular shape or size. One embodiment of the pattern-assisted means is a solgel layer having a pattern. The pattern could be made by embossing, photolithography, or magnetic film etching, or substrate etching.
Another aspect of the invention is a method of surface treating a substrate of a recording medium, comprising forming a solgel layer on the substrate and patterning the solgel layer.
Additional advantages of this invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiments of this invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out this invention. As will be realized, this invention is capable of other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from this invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.